Method for preparing non-metallic surface for metallizing

ABSTRACT

A SINGLE-STEP PROCESS IS DESCRIBED TO REPLACE THE CONVENTIONAL CONSECUTIVE STEPS OF SENSITIZING AND SUPER-SENSITIZING A NON-METALLIC SURFACE PRIOR TO APPLICATION OF A METALLIZING SOLUTION SUCH AS ALKALINE CHELATED COPPER. THE NEW PROCESS COMPRISES SIMULTANEOUS SPRAYING OF AQUEOUS ALKALINE TIN SOLUTION AND AN AQUEOUS SOLUTION OF GLUCONIC ACID AND SILVER SALT.

United States Patent 3,582,392 METHOD FOR PREPARING NON-METALLIC SURFACEFOR METALLIZING Samuel Wein, deceased, late of Quincy, Mass; by DonaldW. Berman, executor, 56 Plain St., South Braintree, Mass. 02185 NoDrawing. Filed Aug. 13, 1968, Ser. No. 752,132 Int. Cl. B44d 1/092; C23c3/02 US. Cl. 117-47 1 Claim ABSTRACT OF THE DISCLOSURE A single-stepprocess is described to replace the conventional consecutive steps ofsensitizing and super-sensitizing a non-metallic surface prior toapplication of a metallizing solution such as alkaline chelated copper.The new process comprises simultaneous spraying of aqueous alkaline tinsolution and an aqueous solution of gluconic acid and silver salt.

BACKGROUND OF INVENTION This invention relates to the chemicaldeposition of metallic films on non-metallic surfaces, as, for example,copper on plastic. Such films are used as such, or are built up inthickness electrolytically or are plated with other metals, dependingupon the particular end use. Such chemically deposited metallic filmsare used in the production of printed circuits, decorative andornamental devices, and in formation of printing elements such aselectrotypes.

The prior art in chemical deposition of metallic films is exemplified byUS. Pats. 2,190,121 and 3,093,509. As taught by this prior art, thenon-metallic surface must be first treated with a sensitizing agentusually containing a tin salt and then treated with a super-sensitizingagent containing gold, silver, platinum or palladium salts in solution.Only after these two steps is the surface ready to adherently receivethe metallizing solution such as the coppering solution.

However, the necessity for the two consecutive separate steps ofsensitizing and super-sensitizing is time-consuming and, hence, raisesthe cost of the process. Accordingly, attempts have been made in thepast to either avoid one or more of these two steps or substitute asingle step. To my knowledge, none of these attempts has beensatisfactory.

One object of this present invention is to provide a means foraccomplishing sensitizing and super-sensitizing in one single step.

Patented June 1, 1971 Other objects and advantages of this inventionwill be apparent from the description and claims which follow.

SUMMARY OF INVENTION This invention comprises generally achieving asingle step method for accomplishing sensitizing and supersensitizing ofa non-metallic surface so as to adherently receive a metal film from ametallizing solution, by simultaneously spraying the surface with bothan aqueous alkaline solution of stannic acid and an aqueous solution ofsilver salt and gluconic acid, followed by rinsing.

SPECIFIC EXAMPLE OF INVENTION A first solution is prepared by dissolvingsix grams of sodium stannate in one liter of water and a second solutionformed by dissolving four grams of silver nitrate and 48 grams of a 50%solution of gluconic acid in one liter of water. Each of these solutionsis then placed in separate reservoirs of a Binks double-nozzle spraygun. The two solutions are sprayed simultaneously onto a vinyl plasticsheet for about five to fifteen seconds. The surface so treated is thenrinsed with water at room temperature. Within about 30 seconds afterspraying a brownish deposit forms on the surface.

A coppering solution is then sprayed onto the treated surface. A typicalcoppering solution comprises copper salt, chelating agent, reducingagent and alkali in water. Suitable copper salts include copper sulphateand copper acetate. Suitable chelating agents include ethylenediaminetetra acetic acid (EDTA) and salts thereof, sodium gluconate andRochelle salt. Suitable reducing agents include formaldehyde andhydrazine sulphate. Specific examples of such coppering solutions areillustrated in US. Pat. 3,093,509, as for Examples IX, XIII, XIV and XV.

I claim:

1. A method for treating a non-metallic surface so as to render itreceptive to an electroless coppering solution, comprising the step ofsimultaneously spraying said surface with both an aqueous, alkalinestannate solution and an aqueous solution of gluconic acid and silvernitrate.

ALFRED L. LEAVITT, Primary Examiner I. A. BELL, Assistant Examiner US.Cl. X.R. "5 117-1055, 106-1; 20430; 11 7-71

